Disc drives are used for data storage in modern electronic products ranging from digital cameras to computer systems and networks. A disc drive typically includes a mechanical portion, or head disc assembly (HDA), and electronics in the form of a printed circuit board assembly (PCBA), mounted to an outer surface of the HDA. The PCBA controls HDA functions and provides an interface between the disc drive and its host. An HDA includes moving parts such as one or more magnetic discs affixed to a spindle motor assembly for rotation at a constant speed, an actuator assembly supporting an array of read/write heads that traverse generally concentric data tracks radially spaced across the disc surfaces and a voice coil motor (VCM) providing rotational motion to the actuator assembly. In operation, the magnetic-recording disc rapidly rotates by the spindle motor to access (read and/or write) the data stored on the disc.
A disc drive unit typically includes a housing that protects the workings of the drive from particulates and other environment-related contaminants. Control of the internal relative humidity (RH) within the housing of the disc drive is desirable since the moisture content of the surrounding air affects the performance and reliability of the head/disc interface (HDI), which is an important parts of the disc drive recording system. For example, it is known that head-to-disc stiction and media corrosion are aggravated by high relative humidity levels. As a further example, excessive disc wear has been observed under conditions of very low relative humidity.
Many commercial hard disc drive products incorporate various elements, such as salts in the form of potassium carbonate/bicarbonate, activated carbon, and other elements to adsorb moisture and volatile organic vapor contaminates (second-type of molecules) within a drive. The adsorption helps to moderate relative humidity levels within the drive. Additionally, desiccants, such as silica gel may be included for further moderation of relative humidity inside the drive. The beneficial effects to such disc drive products are, however, limited to the longevity of the elements used to offset the effect of the environment-related contaminants.
These and other matters have presented challenges to humidity and other molecule removal within an enclosure for a variety of applications.